I've now had this happen 2 times ; am reading in the train on the way home, battery shows half full, put it in sleep mode. Next morning I flip back the cover and the screen shows that I have to charge the battery before I can do anything !?
Is that a known feature ?? Anything that could cause a sudden drain ?
Wi-fi is off, refresh is at 3 pages.

There have been problems with some covers causing battery drain in sleep mode. The problem seems to be with soft covers that can contact the touchscreen as they close, especially those with an inside pocket or flap.

But if the cover touches the screen I should end up on a different page from when I stopped reading ... ? And that isn't the case.
I've got a Gecko cover that has an edge around the screen of about 2mm. so the flap shouldn't touch the screen.
But I'll keep an eye on it or remove it temporarily to see if it helps ...

But if the cover touches the screen I should end up on a different page from when I stopped reading ... ? And that isn't the case.
I've got a Gecko cover that has an edge around the screen of about 2mm. so the flap shouldn't touch the screen.
But I'll keep an eye on it or remove it temporarily to see if it helps ...

A Gecko (not sure which model) was one of the covers with the problem I think. The cover comes into contact as the device is going into sleep mode and so it doesn't always cause page turns. This thread was where those with the issue discovered the cause, it is very long.